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64 terms

Kaplan MCAT OChem Ch. 11: Amines and N-containing compounds

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amine nomenclature
NR3
amine nomenclature
normally have lone pair of electrons
amine nomenclature
classified according to number of alkyl (aryl) group to which bounded (1, 2, 3)
quaternary ammonium compound
N atom attached to 4 alkyl groups has pos charge (bond from lone pair)
amine common name
alkylamine
amine
suffix; -amine
prefix: amino-
N
used to label sub attached to N in 2ndary and 3rd amines

list separate ones for each diff. substituent
aromatic amines
derivates of aniline (C6H5NH2) using common or as derivative of benzeneamine
amides
condensation prod. of carb acid and amines
carbamates
gen. formula = RNHC(O)OR'
carbamates
N attached to carbon, so fall into amide category
carbamates
have O on other side of carbonyl w/ alkyl or aryl group attached to it:

http://upload.wikimedia.org/wikipedia/commons/thumb/4/41/Carbamate-group-2D.png/220px-Carbamate-group-2D.png
carbamates
derived from isocyanates
isocyanates
gen. formula: RNCO
isocyanates
both DB to both oxygen and nitrogen => carbon is polar and can be attacked by Nu:

http://upload.wikimedia.org/wikipedia/commons/2/2b/Isocyanate-group.png
isocyanates
when attacked by alcohol => carbamate
carbamates
urethanes
urethanes
AKA carbamates, and can form polyurethanes
urethanes
useful and versatile polymer
enamines
N analogs of enols, instead of OH, an amine group is attached to C=C (enamines are to N as enols are to O):



http://upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Enamine-2D-skeletal.png/200px-Enamine-2D-skeletal.png
imines
contain N=C:

http://upload.wikimedia.org/wikipedia/commons/e/e9/Imine-2D-skeletal.png
nitriles/cyanides
-C≡N,

prefix: cyano-
suffix: -nitrile
nitro
compounds that contain this group, NO2
az
compound that contains N
diazo
compounds w/ N2 functionality, w/ two Ns at the end of a chain resonating between DB and TB

lose N2 => carbenes
carbenes
highly reactive carbons w/ only 6 valence electrons (usually seen as C w/ two R groups and a lone pair of electrons)
azides
compounds w/ linear N3 functionality (DB between 3 nitrogens)
azides
when loses N2 => nitrenes:

http://upload.wikimedia.org/wikipedia/commons/6/6c/Azide-2D.png
nitrenes
N analogs of carbenes
nitrenes
tend to have 6 valence electrons distributed in one bond to R group and two lone pairs of electrons
AA
are amines

pep bonds between these in proteins are amide bonds
BP of amines
between alkane and alcohols
as MW inc
BP incs
primary and secondary amines
can H bond, not as strong as alcohols
tertiary amines
can't H bond => lower BP
N atom in amine
sp3, three sub to complete and a lone pair => basic and Nu
N atoms
tech chiral due to geo of orbitals

enantiomers can't be isolated because they interconvert rapidly (nitrogen inversion)
nitrogen inversion
inversion of the sp3 orbital occupied by the lone pair

6 kcal/mol => will not be optically active

if at very low temp or if structure prevents inversion of molecule => optically active (ex: quaternary ammonium salts since lack of lone pair)
amines
are bases => readily accept protons => ammonium ions

pKb = 4 (more than ammonia, less than OH)
aromatic amines
like aniline (pKb = 9.42) are far less basic than aliphatic since EW effect reduces bascitiy of amino group
aromatic amines
other groups affect basicity of anilines

EDG => inc. basicity
EWG => red.
amines
WA (pKa = 35), thus SB needed to deprotonate
types of synthesis of amines
Alkylation of ammonia

reduction
types of alkylation of ammonia
direct

gabriel synthesis
types of reduction (amines)
nitro compounds

nitriles

imines

amides
direct (alkylation of ammonia )
alkyl halides + ammonia => alkylammonium halide salts + alkyl halide => more complex products
direct (alkylation of ammonia )
ammonia (Nu) => displaces halide atom (Sn2)
direct (alkylation of ammonia )
salt treated w/ base => alkylamine product
direct (alkylation of ammonia )
often leads to side products: alkylamine as Nu (lone pair and electron donating properties of alkyl group) on N + alkyl halide => complex products
gabriel synthesis
converts a primary alkyl halide to primary amine (sn2, lone pair of ammonia and halide good LG)
gabriel synthesis
first create a disguised form of ammonia (deprotonated phthalimide) to prevent side product formation => phthalimide => displaces halide ion => N-alkylphthalimide => hydrolyzed w/ aq. base => alkylamine
phthalimide
condensation product of phthalic acid and ammonia, good Nu when deprotonated
N-alkylphthalimide
when halide ions displaced => this forms and doesn't react w/ other alkyl halides
reduction of nitro compounds
can reduce this to primary amines
reduction of nitro compounds
most common reagents is Fe and Zn used w/ dilute HCl
reduction of nitro compounds
useful for aromatic compounds because:
1. nitration of aromatic rings is easy
2. this converts deactivating to activating groups
reduction of nitriles
can be this w/ H and a metal catalyst, or w/ LAH => primary amines
reduction of imines (reductive amination)
aldehyde/ketone + ammonia, a primary amine, or a secondary amine => 1, 2, or 3rd amine
reduction of imines (reductive amination)
carbonyl becomes -OH (carbinolamine) => loses water => imine => but when exposed to hydrogen and metal catalyst => reduction to amine
imine
looks like carbonyl => similar polarity and reactivity
reduction of amides
amides can be this w/ LAH => amines
exhaustive methylation/hoffman elimation (reactions)
1. amine w/ excess methyl iodide => quat. ammonium iodide (methyl on N where H used to be)
exhaustive methylation/hoffman elimation (reactions)
2. treatment w/ silver oxide and water => displaces the iodide ion => ammonium hydroxide => WHEN heated => elimination (e2) => alkene and amine
exhaustive methylation/hoffman elimation (reactions)
predominant alkene formed is least sub because of the bulk of quat. ammonium salt LG